1. Field of the Invention
This invention relates to the control of dust that is emitted from aromatic anhydrides. More particularly, this invention relates to the suppression of dust emitted from solid aromatic anhydrides by treating the aromatic anhydride with an organic compound.
2. Prior Art
Aromatic anhydrides are useful industrial chemicals. Many of them are produced and used on the order of millions of pounds per year. For example, trimellitic anhydride (TMA) is used in the manufacture of vinyl plasticizers, which can be used in electrical wire insulation, refrigerator gasketing, automotive padding and upholstery, washable sheeting, and pool liners. TMA is used in water-soluble alkyd coatings. It is used in the production of high-temperature polymers, such as amide-imide polymers. TMA is used as a curing agent for epoxy resins. In addition, its derivatives are used in various specialty applications, such as dye intermediates, heavy duty detergents, agricultural chemicals, and pharmaceuticals. Aromatic dianhydrides in particular are useful for preparing high performance resin materials. However, aromatic anhydrides, particularly finely-divided aromatic anhydrides, are extremely difficult to handle because they emit relatively large amounts of dust. Dust from aromatic anhydrides can be irritating and TMA dust in particular can produce sensitization effects when inhaled.
Since much of the exposure to this dust occurs during the handling of the solid aromatic anhydrides, a suitable method for suppressing airborne aromatic anhydride dust particles is desired.
Various techniques have been used to suppress dust. For example, in U.S. Pat. No. 2,222,370, Mori disclosed a method for preventing and laying dust in coal mines by spraying the coal mine workings with a mixture or emulsion of petroleum oil and water, the water being present in an amount sufficient to make the oil spray noninflammable.
In U.S. Pat. No. 2,399,464, Butcher taught an improved liquid spraying agent adapted to inhibit the surface dusting of the soil in playgrounds, training camps, and dirt walks. The stable liquid dust-laying composition comprised a low-viscosity, low-volatility petroleum distillate oil, naphthenic acid, a wetting agent consisting essentially of a sodium salt of a sulfonated higher alcohol, water, and a germicide.
In U.S. Pat. No. 2,423,449, Heald, et al, disclosed treating soap to reduce dust-forming and lumping tendencies by spraying soap particles with a heavy mineral oil fraction.
In U.S. Pat. No. 2,585,026, Moen, et al, taught the reduction of dust produced by grain during handling by applying to the grain an emulsion of water and mineral oil.
In U.S. Pat. No. 3,913,637, Taylor taught the use of a liquid material such as white mineral oil to reduce the dust in a solid premix concentrate for addition to animal and poultry feed, the concentrate consisting essentially of gentian violet, a selective fungicidal mold inhibitor of "Candida albicaus," and inert ingredients.
In U.S. Pat. No. 4,276,308, Ito, et al, disclosed using a polybutene sticking agent in the preparation of granules containing a carboxylate, the granules being used safely as an effective wood preservative composition.
In Japanese Patent Publications Nos. 80037521, 50053538, and 56059701, there is taught a powdery agricultural agent giving less dusting, which powdery agricultural agent is prepared by mixing the active ingredient with a powdery inorganic carrier and polybutene or polyisobutene.
In U.S. Pat. No. 4,208,433, Darham, Jr., et al, disclosed the use of an oleaginous vehicle, such as corn oil, unrefined cottonseed oil, and soya oil, in the adsorption of dust into whole grain seeds to eliminate grain warehouse explosions, reduce fire hazards, and improve environmental conditions for humans.
In U.S. Pat. No. 4,490,511, Li, et al, disclosed a low-dusting anhydride curing agent blend for epoxy resins, which blend comprised a solid acid anhydride, TMA, and from 1 wt % to about 10 wt % normally liquid anhydride. The liquid anhydride was selected from methyl hexahydrophthalic anhydride, nadic methyl anhydride, and dodecyl succinic anhydride. The TMA flakes can be pre-wetted or the finely-divided TMA powder can be post-wetted with the liquid anhydride to provide the TMA with a greatly reduced dusting tendency.
There has now been found a method for suppressing dust emitted from solid aromatic anhydrides, which method employs the application of an organic compound to the aromatic anhydride that does not appreciably affect the aromatic anhydride in a deleterious manner and is selected from materials that are not liquid anhydrides.